Study of the Mechanism of 7‐exotrig Cyclizations of Aryl, Vinyl, and Alkyl Radicals on Oxime Ethers

Author:

Bejarano Carlos A.12ORCID,Díaz John E.1ORCID,Camacho Jairo13ORCID,Flores‐Bernal Gustavo G.4ORCID,Miranda Luis D.4ORCID,Mejía Sol M.1ORCID,Loaiza Alix E.1ORCID

Affiliation:

1. Department of Chemistry Facultad de Ciencias Pontificia Universidad Javeriana Cra. 7 No. 40-62, Edificio Carlos Ortiz 110231 Bogotá Colombia

2. Department of Chemistry, Facultad de Ciencias Universidad Antonio Nariño Cra. 3 Este No. 47 A-15 110231 Bogotá Colombia

3. Programa de Ingeniería Industrial Facultad de Ingeniería Corporación Universitaria Minuto de Dios – UNIMINUTO Calle 81b No. 72b-70 111021 Bogotá Colombia

4. Department of Organic Chemistry Instituto de Química Universidad Nacional Autónoma de México Circuito Exterior S. N., Ciudad Universitaria 04510 Mexico City Mexico

Abstract

AbstractIn this work, we conducted a study of 7‐exotrig cyclizations mechanism involving aryl, vinyl, and alkyl radicals on oxime ethers. Initially, the reaction of brominated oxime ether 9 a with (TMS)3SiH and AIBN gave rise to aryl radicals that underwent a 7‐exotrig cyclization on the oxime ether, yielding dibenzoxepine 10 a, and the ipso reaction and reduction products were obtained as well. Approximate rate constants at 80 °C for the 7‐exotrig (1.0×108 s−1) and the ipso cyclization (4.3×107 s−1) were determined by competition experiments. DFT calculations showed good agreement with the experimental results. The reduction rate constant of the N‐alkoxyaminyl radical with (TMS)3SiH was calculated to be 4.1×10−1 M−1 s−1; while the rate constants for the 7‐exotrig cyclizations of vinyl and alkyl radicals on the oxime ether were estimated in the ranges of 106 s−1–108 s−1 and 103 s−1–108 s−1, respectively. The 7‐exotrig cyclization reactions involving aryl, vinyl, and alkyl radicals with oxime ethers were found to be an exothermic and irreversible process, with the oximic carbon showing a preference for nucleophilic alkyl radicals. This kinetic study contributes to the deeper understanding of radical‐mediated cyclizations, enabling the efficient design of complex synthetic routes.

Funder

Pontificia Universidad Javeriana

Ministerio de Ciencia, Tecnología e Innovación

Publisher

Wiley

Subject

Organic Chemistry,Physical and Theoretical Chemistry

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